Transmission Problems...Help please

[hillbillycountry2007]

I have a 1988 Ranger 2.9 6cyl super 4x4 auto transmission with pushbutton four-wheel drive. I am having overdrive problems. I kicks in and out every once in a while but i am wondering on how to fix it. Like is it electronic or mechanical? First of all i would like to know whats actually wrong with it. if any one can help please do.
thanks

 

[baddis]

check for codes. it could be the 3/4 shift solonoid or it could be a missajusted tv cable or it could just be wore out. the computer will tell about the 3/4 solonoid.